Depending on where you are getting them from and the ages of them, make sure you quarantine them as appropriate - piggies from anywhere other than a reputable rescue centre should ideally be quarantined in a separate room for two weeks to ensure they don’t pass anything on to your piggy. However, quarantine should not be done if your piggy is under four months of age or in acute pining. In those circumstances you bond straight away because the social needs of the single piggy is greater than the need to quarantine.
Claire has linked in the bonding guide Which tells you the procedure for carrying out a bonding.
I hope all goes well! Keep us posted